In seat belt systems for automotive vehicles employing retractable shoulder belts it is common practice to employ a "comfort feature" which relieves spool spring windup pressure from constant application to the occupant's shoulder belt. After initial belt extension to accommodate the occupant's size, seat position, buckling and spring retraction to take up slack in the shoulder belt, the occupant may extend the belt slightly to a pressure relief position whereupon a comfort lock engages to prevent spring retraction tension from causing discomfort to the occupant. Standard functional requirements for the comfort lock feature include the following:
1. the belt webbing from the retractor must extend to a working range of the belt with approximately 25% (61/2") still wound on the spool; PA1 2. the belt should then retract under spring windup tension a minimum of 6" to the occupant's normal restraint position (12.5" on spool); PA1 3. extraction of the belt in the order of 1" should engage the comfort lock to prevent retraction; PA1 4. subsequent extraction, to accommodate reaching to the instrument panel or glove compartment, in the order of 4" should be possible followed by return of the belt to within 1" of the comfort lock position previously set without releasing the comfort lock for full retraction; PA1 5. extraction of the belt from comfort lock position a distance exceeding that for normal maneuvering, e.g. in the order of 6", followed by release should cause the belt to fully retract without locking.
Such requirements have been met in at least two basic systems. One is known in the art as a ratchet scroll/scroll follower system such as shown in U.S. Pat. Nos. 4,002,311, 4,165,054 and 4,149,683. The second type, preferred by applicants, involves the use of spring loaded friction elements to control pawl engagement and release of a comfort lock, under required conditions of webbing extraction and release, such as shown in U.S. Pat. No. 3,834,646 reissued as RE. 29,095, 4,060,211 and 4,053,116.
One of the problems encountered in such comfort feature systems is the possibility of the comfort lock retaining the shoulder belt in extended position upon buckle disengagement by the occupant in leaving the seat so that free webbing may hang out of the car upon door closure or otherwise fail to retract when a new occupant enters and buckles the seat belt. One answer to this problem has been to provide an electro-magnet or mechanical door opening responsive release for the comfort lock so that full shoulder belt retraction will occur whenever the occupant opens the door to leave the seat. Such comfort lock release systems involve substantial expense and complexity due to the remoteness of the actuating linkage relative to the shoulder belt takeup spool. Accordingly, similar less expensive systems for releasing the comfort lock have been sought by those involved in the art with various suggestions for sensing means which would reflect occupant departure from the seat, e.g. sensing means responsive to automatic retraction of the lap belt on a separate spool which is not equipped with a comfort lock and accordingly is always automatically retracted upon occupant unbuckling to leave the vehicle seat. Applicants' have responded to this suggestion and pursued this approach in developing the present comfort lock release which is simpler, less expensive and more dependable than any known in the prior art.